Blood Culture Techniques: Increasing Yields and Reducing Contamination

Bloodstream infections are associated with significant patient mortality and health care costs. Isolation of the causative organism will direct the clinician to institute specific treatment. But isolation of the implicating organism is hampered by lack of yield and increased level of contamination. The rates of contamination and reduced yield are more relevant in Sri Lanka as most of our public sector laboratories use manual blood culture system and do not adhere to correct aseptic techniques of blood collection. This has led to delay in identifying the causative organism. Increase rates of contamination not only have hindered specific treatment but also have prompted clinicians to use antibiotics of increased cost and toxicity. Though differentiation between true pathogen and contamination is not clearly set, certain parameters, namely identification of the organism, proportion of the positive blood culture sets, Number of positive blood culture bottles within a blood culture set, time to growth, source of cultures (catheter drawn versus percutaneous) along with clinical and laboratory clues might help the clinicians and microbiologist to make a reasonable conclusion. Proper skin preparation with correct disinfectants, adherence to recommended techniques and contact time along with the collection of optimal volume of blood through a peripheral vein by a trained phlebotomy team has been found to increase the yield and reduce the rates of contamination. These recommendations could be practiced with ease in resource poor settings similar to Sri Lankan public sector hospitals.